PC to Home Theater: Audio Decoding on PC or Receiver?

[filmhappy]

I am looking to buy a PC to use with my 5.1 home theater system. I looked around and got sort of an idea that the PC used in this purpose should have a digital or optical audio output, and then I can connect PC and my receiver with a coaxial or an optical cable.

The one remaining question I have is: if I use a coaxial cable to connect the digital output from PC to the digital input to my receiver, can I still decode the audio signals on my PC and send over the multi-channel signals through one single digital cable? Or now I have to have separate connection for each channel, which means 6 connnections for my 5.1 system? The reason I ask the question is that a lot of movie files (rm, avi, etc.) whose audio signals (eg. AC3 5.1) can only be decoded on my PC and not probably by my receiver.

Any information is appreciated. Thanks.

[sorinicu]

AC3 is compatible with DolbyDigital on your receiver.
The only problem that you will have (connecting the PC to the receiver digitally) is that all the sounds in games and such will be only stereo PCM (unless you buy a card with DolbyDigitalLive or DTS Connect like the one from Azuntech).

[redwudz]

It sounds like your present receiver doesn't do the AC3 decoding, unless it has optical or coaxial inputs. The audio sent from the computer or the sound card, in particular over optical or coaxial leads, is generally encoded with all the channels.

I have a older receiver I don't use anymore that has the individual 5.1 inputs. With it, the DVD player converted the signal to the individual channels. Most all the newer receivers do the decoding in the receiver from a single coaxial or optical input. If the signal isn't AC3 5.1, then it usually just comes out as stereo.

[edDV]

Even if you have the coax or optical S/PDIF connection to a receiver with a Dobly Digital AC3 decoder, the result will still be simple stereo unless your DVD player software or DTV tuner support AC-3 demultiplex and feed the AC-3 result through the motherboard S/PDIF port to the receiver for decoding.

If the computer decodes to 5.1, then you would need to reencode to AC-3 before it could be sent over coax or optical.

This usually only happens for games.

[jsmithepa]

The reason I ask the question is that a lot of movie files (rm, avi, etc.) whose audio signals (eg. AC3 5.1) can only be decoded on my PC and not probably by my receiver.

I dunno what movie files yer talking about, but when I play DD/DTS DVD on my PC, my Sigma Designs xCard sends the AC3 signal as-is, to my receiver, via coax to be decoded on the receiver.

The AC3 cable, doesn't matter coax or toslink transports an encoded/multiplexed signal. If u want your PC card to decode, then it will have to be re-encode to go through that AC3 cable, which, as you sense, doesn't make sense.

If your sound card/board has a coax/toslink out, then it's sending the signal as-is without decoding. If it has 6-8 discreete analog outs, then it's decoding internally and sending out the 6-8 analog channels out to be amplified.

[filmhappy]

Thank you all for the valuable information.

My receiver is pretty new and does handle the Dolby digital signals, so it should be able to decode AC3 5.1. I will just need to find myself a PC with the right sound card with coax or digital output.

Thanks again!

[snipper_cr]

Make sure that you have both your software and hardware set up properly to digital pass through.

For example on my system: If I wanted the DVD program to use software decoders, I would make sure the program is set for software (this is for if you do not have a sound card that can do dolby digital orDTS). You would then output each channel to your receive (via the Center, Left/Right, SR/SL plugs)

If you want your sound card to do the decoding, make sure you set the player up to properly do this. For instance, in WinDVD7, select S/PDIF Pass through to external device. This tells the software to pass the AC3 audio to the sound card for decoding. Then the sound card output to your receiver via the center, Left/Right, SR/SL plugs. With an Audigy 2 ZS card, you know the sound card is decoding because an onscreen Dolby Digital (or DTS) logo will appear.

Finally, if you want to have the decoding done by the receiver, make sure your software is still set to S/PDIF pass through. THEN set your sound card to S/PDIF pass through. In my case (Audigy 2 ZS Plat), I go into the Device HQ, and go under decoders. Here I set the S/PDIF pass through. You know it is set up properly if during AC3 playback you see "Bitstream" logo show up.

Hope this makes some sense.

[popinadam]

For the life of me I can't get my set-up to work how i'd like. I'm also as above trying to get some AC3 5.1 Avi files to function properly with my receiver but i'm not sure if it really can handle them. The receiver is a JVC RX-6000V. I have an Audigy 2 ZS Gamer. The're connected Digitally with one Hosa Digital Coaxial and one Hosa Rca Female -> 3.5 Mm Male Mono adapter. The dvd playback 5.1 works perfect with WMP10 but i'm not really sure what prog I can use to get these AC3 5.1 files running. I'd prefer them to play in WMP but i'm not holding my breath. So far they just play in Stereo sound which is sufficient for now but not to the extent I think is possible. If I can get some addition help from someone with this i'd appreciate it.

[sorinicu]

The're connected Digitally with one Hosa Digital Coaxial and one Hosa Rca Female -> 3.5 Mm Male Mono adapter. The dvd playback 5.1 works perfect with WMP10 but i'm not really sure what prog I can use to get these AC3 5.1 files running. I'd prefer them to play in WMP but i'm not holding my breath. So far they just play in Stereo sound which is sufficient for now but not to the extent I think is possible. If I can get some addition help from someone with this i'd appreciate it.

You have to set your player to send the signal via SPDIF not via the analog outputs. The WMP cannot have that option so when you play your AC3 files, the WMP sends those to be decoded by Audigy2 driver. The card then outputs the surround sound via analog outs or as stereo PCM via digital out (card cannot reencode back to DolbyDigital).
You will need a player that supports the setting of SPDIF out - WinDVD or VLC media player are some options.
PS: Try a STREO adaptor for your config, and the white RCA will be SPDIF out. And there are called jacks not hosa

[ba5e]

PS: Try a STREO adaptor for your config, and the white RCA will be SPDIF out. And there are called jacks not hosa

LOL hosa is a brand......a pretty good cable brand....